DE1521439C3 - Deductive copper plating bath - Google Patents

Description

is usually between about 5 μg / l and 500 mg / l. In any case, it must be ensured that the concentration is kept so low that the desired Metal deposition process at catalytic centers not hindered or brought to a standstill will.

With the aid of the baths according to the invention, the copper deposition takes place at a constant deposition rate Possible perfectly on all catalytic surfaces. Proves to be particularly beneficial it is thereby that the thickness of the deposited 'metal layer over the whole with the bath liquid surface in contact is constant, and! although completely independent of their spatial Design. The baths according to the invention are suitable

therefore with advantage for copper plating of compli-; ornamentally shaped components, which are electroplated with The help of known baths is difficult or hardly possible.

The surface of metals, including nickel, ao cobalt, iron, steel, palladium, platinum, copper, · bronze, manganese, chromium, molybdenum, tungsten, titanium, 'J) tin, gold and silver, has a catalytic effect, whereas materials such as z. B. glass, ceramics, various plastics and paper are usually not catalytic. In order to make the surface of such materials catalytic, the surface is either coated with an extremely thin film of a catalytic metal, e.g. B. palladium, coated or equipped with particles that have catalytic properties or otherwise provided with active centers. As soon as a first layer of the copper to be deposited lies on a catalytic surface, this then acts itself catalytically for the further metal deposition process. The bath according to the invention is therefore also suitable for metallizing a wide variety of non-metallic surfaces of the most varied types, e.g. B. those of silicone, phenolic and epoxy resins, styrene and acrylic resins, polyvinyl chlorides, polyamides, polyesters, ζ. B. those made from ethylene glycol and terephthalic acid, and acrylonitrile-butadiene-styrene resins.

) /) It has proven to be useful while the bathroom is in operation proven the concentration of copper salt and other consumed components accordingly to supplement the deposited amount of metal and to keep the bath concentration constant.

It has also proven to be useful to add a small amount of the bath solution, e.g. B. less than 5 g / l to add a surface-active compound. Typical suitable compounds of this type are e.g. B. organic phosphate esters and sodium oxyethylate. Autocatalytic copper plating baths according to the invention find a wide range of applications, from copper coating for decorative purposes to improving the mechanical properties of molded bodies and the designation of the same to the production of metallic conductors for the. Electricity transport on non-conductors is enough.

. The following examples are intended to further illustrate the invention explain.

Examples Ibis3 (comparative examples)

Copper plating baths were made that were free

of cyano compounds and had the following • compositions and properties:

example 1

Copper sulfate 0.05 mol / l.

Diethylenetriaminepentaacetic acid 0.05 mol / l

Sodium borohydride 0.01 mol / l

pH 13

Temperature 25 ° C

Example 2

Copper sulfate 0.05 mol / l

Diethylenetriaminepentaacetic acid 0.05 mol / l pH before adding a

Sodium borohydride solution .... 12 sodium borohydride solution,

consisting of a 6%

Borohydride solution in aqueous

Sodium hydroxide 30 ml / 1 to 10 ml / 1

Example 3

Copper sulfate 0.05 mol / l

Diethylenetriaminepentaacetic acid 0.05 mol / l pH before adding a sodium borohydride solution,
consisting of a 6% borohydride solution in aqueous
Sodium hydroxide 5 ml / 1

The baths according to Comparative Examples 1 to 3 did indeed lead to shiny copper deposits, however, they tended to self-decompose even after a relatively short period of operation, and besides, they were The deposited metal layers are brittle and not very ductile.

For example, 14

A bath was prepared according to the invention, its composition and rate of deposition were as follows:

Copper sulfate 0.05 mol / l

HEDTA, 0.12 mol / l

Sodium cyanide 0.008 mol / l

Sodium borohydride 80 mg / 1

Deposition rate .. 0.1 μ / η

The bath containing the cyanide additive was extremely stable and produced ductile copper deposits.

Example 1 5

To carry out comparative tests, three copper plating baths were produced, of which

Bath (a) in addition to a cyano compound formaldehyde as a reducing agent according to OE-PS .227 055 contained

Bath (b) in addition to a cyano compound borohydride as reducing agent according to the present invention contained and

Bath (c) no cyano compound, but borohydride as reducing agent according to the comparative examples 1 to 3 contained.

The composition of the baths was as follows:

Bathroom (a)

HCHO bathroom with CN "

according to the status of

technology

Bathroom (b)

Borohydride bath

with CN ~ according to

invention

Bathroom (c)

Borohydride bath without CN according to

Comparative example 1 to 3

Na ₅ DETPA *)

Copper sulfate

pH

NaBH ₄

HCHO (37% solution)

NaCN

water

65 g / l
12.5 g / l
13th

6 ml / 1

20 mg / 1

compensation

65 g / l
12.5 g / l
13th
0.4 g / l

20 mg / 1
compensation

65 g / l
12.5 g / l
13th
0.4 g / l

compensation

*) Diethylenetriaminepentaacetic acid, pentasodium salt, 41% solution.

In bath (a) the number of moles of formaldehyde was chosen so that its reducing hydrogen corresponds to that of borohydride was equivalent.

Weighed test pieces made of stainless steel plates with a ^{surface area of 10 cm 2} were sensitized with the aid of a complex palladium salt in a conventionally known manner, after which they were treated in 100 ml portions of the respective baths for 16 hours at about 23 ° C. After the test specimens had dried, they were visually checked for the appearance of the copper precipitate and weighed again in order to determine the increase in weight of each individual test specimen caused by copper deposition. The numerical values obtained were divided by 8.9 (the specific gravity of copper) and ^{multiplied by 10 3} , whereby the thickness of the coating was determined in microns.

The following results were obtained:

The test specimens copper-plated with bath (a) (formaldehyde-cyanide bath according to the state of the art) showed a copper plating 1.3 microns thick. Parts of the test specimens were completely free of Copper deposition. The copper deposited on the surface showed blistering and was easy to peel off, d. that is, its adhesion was poor.

ao The one with bath (b), the borohydride-cyanide bath according to the invention, Copper deposited was 1.6 microns thick. The copper-plated ones Test specimens showed a bubble-free appearance that was uniform on all sides, homogeneous and completely light pink Surface coating.

When using the cyanide-free borohydride bath (c), the thickness of the copper layer was 0.7 microns. the Although test specimens were uniformly copper-plated on the surface, the appearance of the surface was dark orange, d. that is, the copper was partially oxidized. No blistering was observed. The results show that the bath according to the invention differs from the copper plating baths used hitherto in particular by an increased deposition rate of the copper on the surface of the Objects to be copper-plated, through an improved and, in particular, more uniform coating formation as well as by improving the adhesion of the copper coating deposited on the surface, which leads to a longer shelf life of the same.

Claims (4)

1 2 The invention is based on the knowledge that claims: The specified object can be achieved in that the copper plating bath in addition to a reducing agent 1. Reductive copper plating bath, which is incorporated into a type of boron compound based on a water-soluble copper salt and a cyano compound to form 5,
The reductive copper plating bath according to the Erten complexing agent for copper ions as well as a discovery is characterized in that a compound is used as the reducing agent which identifies that the reducing agent is a group of Alkali borohydrides or the aminoborane bond is used, which belongs to the group of io, and that the bath solution contains a small amount of alkali borohydrides or the aminoboranes, a cyano compound is added. and that the bath solution contains a small amount of a The bath according to the invention for electroless copper Cyan compound is added. The deposition preferably contains reducing agents 2. Bath according to claim 1, characterized marked borohydrides, as these interact with net that the reducing agent in an amount of 15 suitable complexing agents to mask the 0.0002 to 2.5 moles / liter is present in the bath. Copper ions in an economical way for reduction 3. Bath according to claim 1, characterized in that the metal cation on catalytic surfaces is net in that the cyano compound has a low inorganic tendency to spontaneous reaction.
Is cyanide or an organic nitrile. All water-soluble borohydrides are suitable 4. Bath according to one of claims 1 to 3, da- 20 a good solubility product and characterized by sufficient that the concentration of stability in aqueous solutions. Sodium or potassium boro liters have proven to be particularly suitable as cyanide compounds between 5 μg / liter and 500 mg / and are not sufficient to produce the autohydrides. Also useful are sub- 'catalytic metal deposition on catalytically substituted borohydrides, z. B. to hinder sodium trimethoxyboro-effective surfaces or to 25 hydride, NaB (OCH ₃ ) ₃ H, and aminoboranes, z. B. Bring to a standstill. Isopropylamino and dimethylaminoborane. To prevent oxidation of the borohydride, the bath solution is preferably used at a relatively high pH at a pH value between 10 and 14, 30 turns. The baths according to the invention consist, for. B. from water, a water-soluble copper salt, a Complexing agent to mask the copper salt, a borohydride as a reducing agent and a The invention relates to a reductive copper-cyanide compound, the pH, e.g. B. with bath containing a water-soluble copper salt and sodium hydroxide to a suitable value Formation of water-soluble stable copper complexes, preferably between 10 and 14, is set. the Capable complexing agents for copper ions as well as amount of essential bath components can be in contains a reducing agent. vary widely, but typical der- The use of boron-containing reductions- 40-like baths has approximately the following composition: averaging in the reductive metal deposition has been since
long known, z. B. the use of amine bora water-soluble nen and alkali borohydrides (compare e.g. the US-PS copper salt 0.002 to 0.60 mol / l, 30 63 850 and 30 91 554 as well as GB-PS 945 018). Complexing agent 0.7 to 10 times the t Baths of this type, however, are not capable of fully loading 45 moles of the copper salt, because they are not stable enough and for reducing agents .... 0.0002 to 2.5 mol / l, They tend to self-decompose and since they also lead to a qualitative cyano compound 5 μg / l to 500 mg / l, insufficient, especially brittle metal layers alkali metal hydroxide sufficient for setting to lead. development of a pH value of There has therefore been no lack of attempts to 50 10 to 14. to remedy the disadvantages shown (reference is e.g. on GB-PS 9 56 922 and 910 709 and US-PS Theoretically, V ₄ to Ve moles of borohydride per 29 76180 and 29 76 181), but it was not possible to use one mole of copper salt, this amount being considered autocatalytic bath for reductive copper lower limit is to be considered. The amount of complex separation to create the forming with improved stability depends largely on its type and not without Loss of deposition rate too much beneficial, also of the concentration of the serted copper coatings, particularly with respect to copper salt. In an alkaline solution, that's before ductility and durability, leads. added relationship between copper salt and complex The object of the invention is to provide a reductive builder between about 1: 1 and 1:10. A minor one indicate copper bath, which is characterized by a strong 60 excess of complexing agents, based on the amount Characterized by improved stability and with an increased lack of copper salt present, is fundamentally an advantageous rate of separation Copper plating supplies that do not adhere. brittle, but very ductile and also independent. The spatial design of the surface and connections are particularly advantageous they are applied, of uniform thickness, 65 adhesive way around inorganic cyanides or nitriles, are bubble-free, pure and shiny and next to a z. B. sodium or potassium cyanide, glycolonitrile, improved appearance improved adhesive strength lactpnitrile and α-hydroxynitrile, e.g. B. a-Hydroxyiso- and thus have an improved shelf life. butyronitrile. The concentration of the cyano compound